Some 2015 to 2016 Cadillac, Chevrolet and GMC vehicles equipped with the 8L45 or 8L90 transmission may have a complaint of delayed engagements into drive or reverse after sitting with the engine off for several hours or overnight. The complaints may also be what appears to be a no movement condition or transmission slippage.
The transmission fluid is draining back into the sump from the torque converter. After start-ing the engine, the time it takes the transmis-sion fluid pump to fill the torque converter is where the complaint originates. One cause for this may be a problem with the original pump design.
Install a new design level stator support as seen in Figure 1, which has an additional check ball capsule located in the torque con-verter clutch release oil circuit to prevent a drain-back condition and the above-mentioned complaints.
8L45 Stator Support ………………..24277230
8L90 Stator Support ………………..24277234
Full size trucks and sport utility vehicles may have a complaint of a whining noise in fourth and fifth gears.
The reaction carrier (Figure 2), was machined incorrectly. The pinion gear pins were placed slightly off center. This causes a mating problem with the reaction internal gear (Figure 2). If this condition is allowed to exist, eventual failure of the carrier pinion gear bearings will occur.
Replace the reaction carrier with the updated design level part. Remove the spiral snap ring from the output carrier internal gear. With the snap ring removed, the reaction carrier can now be separated from the internal gear as seen in Figure 2.
Updated Reaction Carrier ……………………24275296
Some 8L90 transmissions may have a complaint of a whistling noise whenever the vehicle is running.
The 50t orifice in the spacer plate, which is an exhaust for the converter feed limit oil circuit, is too small.
Enlarge the 50t orifice from its original size of .030” (0.75mm) to .067” (1.70mm) as shown in Figure 3. If a new spacer plate assembly is required, use the part number under “Service Information.” Check the 50t ori-fice in the replacement spacer plate assembly to be certain it is .067” (1.70mm) in diameter.
8L Space Plate Assembly ……………………24273682
Some GM vehicles can sustain body control module (BCM) internal damage if the module ground path is removed while the module is still supplied with power (see Figure 4 for BCM view). In addition, other sys-tems controlled by the BCM will also be affected such as inoperative or intermittent in one or more of the fol-lowing systems:
1 – Interior lighting will remain on or will not work.
2 – Remote keyless entry inoperative.
3 – Inoperative door locks.
4 – Remote vehicle start inoperative.
5 – Remote trunk release inoperative.
The following vehicles are susceptible to this issue:
2006 – 2011 Buick Lucerne
2008 – 2014 Buick Enclave
2006 – 2011 Cadillac DTS
2007 – 2009 Cadillac SRX
2007 – 2014 Cadillac Escalade
2008 – Cadillac CTS
2006 – 2008 Chevrolet Monte Carlo
2006 – 2013 Chevrolet Impala
2007 – 2009 Chevrolet Equinox
2007 – 2013 Chevrolet Silverado/Avalanche 2007 – 2014 Chevrolet Suburban/Tahoe 2008 – 2014 Chevrolet Express Van 2008 – 2014 Chevrolet Traverse
2007 – 2013 GMC Sierra
2007 – 2014 GMC Acadia/Yukon
2008 – 2014 GMC Savana Van
2007 – 2009 Pontiac Torrent
2007 – 2010 Saturn Outlook
2008 – 2010 Saturn Vue
2008 – 2010 Hummer H2
When attempting to diagnose an electrical circuit problem with the ignition on, should the BCM ground circuit become disconnected from it’s ground point while it is powered up (Figure 5), will cause internal damage to the module.
Some vehicles have the BCM ground circuit wired through another component, this would also result in internal BCM damage. Examples of such vehicles are as follows:
- 2008 – 2010 Hummer H2-The BCM ground path runs through the instrument cluster.
- 2008 – 2010 Saturn Vue-The BCM ground path runs through an instrument panel splice pack.
Be sure to check appropriate wiring diagrams in order to see how the BCM ground path is wired to avoid having an open ground path during electrical diagnostics (see figures 6 through 9). At all other times disconnect the negative battery terminal to avoid the possibility of damage to the BCM.
Some of the above vehicles may have a redundant BCM ground circuit, check the appropriate wiring dia-gram for the vehicle being repaired to be sure before diagnostic work proceeds.
August 2019 Issue
Volume 36, No. 8
- GM 8L45/90: Delayed Engagement After Prolonged Inactivity
- GM 8L90: Gear Whine in Fourth and Fifth Gears
- GM 8L90: Whistling Noise
- GM Body Control Module: Ground Loss Module Damage
